Late last month, 4,000 gallons of Charles River water were transported to a Foxborough facility. There, Desalitech, a Newton-based company, purified the water with a patented reverse-osmosis process.

In coming days, the now-treated water will be delivered to participating breweries for production.

If the concept of river-water booze sounds vaguely familiar, it is. It’s a variation of an event that was part of the 2015 HUBWeek, when Harpoon Brewery produced 18 kegs of pale ale made from Charles River water.

This year, though, organizers wanted to expand, and after the buzz Harpoon drew last year, putting together a lineup of breweries wasn’t difficult, said Alex Goldstein, a Desalitech spokesman.

The breweries have been given free rein to use the water to produce any kind of beer they like, from ales to stouts to IPAs. They’ll be judged separately by both the public and a panel of judges.

Dylan L’Abbe-Lindquist at Cape Ann Brewing Company has already settled on an approach.

Every fall for the past seven or so years, he has produced a brew called Home Port Pale Ale. The idea is to make it as local as possible — the hops, for instance, are grown behind the pub and at his home — and the public is invited to an annual hops-picking event.

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When L’Abbe-Lindquist learned of Cape Ann’s participation in Brew the Charles, he decided to merge the two projects to create an even more locally sourced brew than usual.

“Tying these two things together sort of makes it a little bit easier, and also sort of brings everything full circle,” he said.

At Ipswich Ale Brewery, director of sales and marketing Carla Villa says they’ll be using the Charles water to create the brewery’s first-ever Octoberfest beer. And while Idle Hands’s Tkach declines to go into detail, he does allow that his brewery will showcase the presence of the river water.

“We don’t want to load the beer up with hops that might mask some of the quality of the water it’s brewed with, the purpose of what it is,” Tkach said. “It may not be a popular decision from the competition aspect, but we had two or three different ideas and we narrowed it down and thought this is the way we should go.”

Aside from the event’s more novel aspects, the overarching goal is to highlight the need for sustainable resources.

“What we’re trying to do here, in the greater scheme of things, is we’re trying to bring it to the attention of the public and decision-makers that water efficiency is important,” said Nadav Efraty, chief executive of Desalitech, who points out that a portion of the $25 entrance fees will go to the Charles River Conservancy. “And that we as a society need to think of our water resources.”